CA1040266A - Device for measuring the mass of particles of an aerosol per volume unit - Google Patents
Device for measuring the mass of particles of an aerosol per volume unitInfo
- Publication number
- CA1040266A CA1040266A CA243,196A CA243196A CA1040266A CA 1040266 A CA1040266 A CA 1040266A CA 243196 A CA243196 A CA 243196A CA 1040266 A CA1040266 A CA 1040266A
- Authority
- CA
- Canada
- Prior art keywords
- measuring
- point
- conduit
- particles
- receiving electrode
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/02—Analysing fluids
- G01N29/036—Analysing fluids by measuring frequency or resonance of acoustic waves
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/025—Change of phase or condition
- G01N2291/0256—Adsorption, desorption, surface mass change, e.g. on biosensors
Abstract
ABSTRACT OF THE DISCLOSURE
The specification describes an improved method and apparatus for measuring the density of an aerosol. The apparatus generally includes a housing containing a planar surface, whose resonant frequency is dependent upon a deposit of aerosol particles, and a metallic point whose axis is perpendicular to the planar surface. The deposit of moving aerosol particles on the surface is normally caused by a high voltage electric current between the surface and point but rather than connecting the point to a negative terminal it is connected to a positive terminal. This has been found to provide unexpected advantages and overcomes draw-backs of prior art devices as described in the specification.
The specification describes an improved method and apparatus for measuring the density of an aerosol. The apparatus generally includes a housing containing a planar surface, whose resonant frequency is dependent upon a deposit of aerosol particles, and a metallic point whose axis is perpendicular to the planar surface. The deposit of moving aerosol particles on the surface is normally caused by a high voltage electric current between the surface and point but rather than connecting the point to a negative terminal it is connected to a positive terminal. This has been found to provide unexpected advantages and overcomes draw-backs of prior art devices as described in the specification.
Description
1~4~)X~t~6 The present invention is related to a device for measuring the mass of particules of an aerosol per volume unit.
Various devices are known which make use of the fact that certain substances have the property to present a determined resonance frequency for a given geometric configuration, said resonance frequency being bound to vary when the configuration is modified, especially under the effect of a deposit of particles. In these known devices the deposit of moving aerosol particles on a planar surface of a body, called measuring body, is caused by the passage of a high voltage electric current, between a metallic point and the planar surface of the measuring body, said surface being perpendicular to the axis of the aforementioned point and being ~ partially covered by a planar receiving electrode. The end of the pointi is separated from the planar surface by a distance greater than the spark ~ length in the atmosphere. In these devices the resonance frequency of ! 15 the measuring body is compared to the resonance frequency of a reference ! body maintained in similar temperature and pressure conditions and on the surface of which no deposit is formed.
In the various types of known devices, the reference body is placed in the clrcuit of derived air, and there is a risk of formation of a residual deposit which may modify the configuration of the reference body.
Furthermore, the air flow is initiated by a suction pump which ~s generally ~ arranged at the end of the circuit; the output rate of such an installation j may undergo the influence of variations which are independent from the ! ~ rate of precipitation of the particles.
¦ 25 In these same devices the metallic point is connected to the negative ~ -~: :
1 -2- ; ~ -' ' ' ~, .
, . .. - , , . ,,, . . . .. ~ . : ..
104(~266 terminal of a high voltage electric current generator and the planar receiving electrode is connected to measuring means adapted to measure the resonance frequency of the measuring body. On account of this arrangement, fractions of material are detached from the point, which results in modifying the configuration of the latter. These modifications of the configuration of the point result, in turn, in modifications of the intensity of the dispensed current, these latter modifications causing generally the efficiency of particle precipitation on the planar surface of the measuring body to decrease. Nothing can prevent these current intensity variations from occurring, since the high voltage current sources are voltage-controlled, but not intensity-controlled.
The instant invention allows these drawbacks to be overcome. By connecting the point to the positive terminal, the induced air flow, which is also called "electrical air flow" or "electrical wind" and which may occur in the known devices becomes sufficiently powerful so that it is no longer necessary to rely on the action of a suction pump, especially when taking into account the fact that the passage through which flow the air loaded with aerosol particles has been designed in such a manner that the pressure losses are reduced to a minimum.
When the point is connected to the positive terminal of the high voltage generator, the configuration of said point changes very slowly? and thus the resulting current variations are minimized. Nevertheless, with a view to obtain a still more constant deposit formation efficiency, it is advantageous to provide a current intensity control or regulation of the -feeding current.
: , ' , ' ' ' ~ '.'' .. . . .
. : ... : . , '. ', , ' - . .', . ~,'. . - . ... ~ . . .
lU4~;6 A device for measuring the mass of the particles of an aerosol per volume unit comprises :
- a solid body, or measuring body, having a resonance frequency and comprising a planar surface partially covered by a planar particle receiving electrode, said resonance frequency being a function of the mass of the deposited particles;
- measuring means for measuring the resonance frequency of said solid measuring body, especially as compared to the resonance frequency of a second solid body, or reference body, having the same characteristics as said measuring body and being maintained in the same temperature and pressure conditions as said measuring body;
- means for generating a flow of air loaded with particles and for directing said air flow toward said planar receiving electrode; and - means for electrically loading said particles with a polarity opposed to that of the planar receiving electrode.
In the device according to the invention the means for generating a flow of air loaded with particles and for directing said air flow toward the planar receiving electrode, as well as the means for electrically loading said particles with a polarity opposite to that of said planar receiving electrode are constitùted by a metallic point the geometrical axis of which is perpendicular to said planar receiving electrode, and which is separated from said planar receiving electrode by a distance of about 3 to 15 mm, said point being connected to the positive terminal of a source of electric current delivering a direct current of very high voltage, whereas said planar receiving electrode is connected to measuring means adapted to measure :
. : .
, . ,, -- . . . . . - - ..
, - - , - .: : ..
- . . . - . . . . .
, the resonance frequency of said measuring body, said point and said measuring body being arranged within a measuring conduit coaxial to said point, said measuring conduit com-prising an air inlet nozzle opening near the end of said point, an axial aperture opening into the atmosphere being provided at a location opposite said point, and the assembly of said measuring body,said point and said measuring conduit constituting a measuring cell.
The solid reference body may be arranged in a space called reference space which is entirely closed, and which may be constituted by a conduit similar to the measuring conduit or by a conduit having the same characteristicæ as those of said measuring conduit, the air inlet nozzle and the axial aperture being closed ~n these various embodiments.
When the reference space is constituted by a cell having the same characteristics as those of the measuring cell the air inlet nozzle and the axial aperture of which are closed, it is possible, too, to u~e alternatively each - one of said cells as a measuring cell or as a reference cell. Due to this possibility the instant device presents a considerable flexibility of use and optimum control and calibrating capacities.
In a preferred embodiment the direct current source is provided, for each cell, with current intensity control means regulating the delivered current, said control means comprising more particularly means for maintaining said current intensity at a constant value. Convenient control means of this kind which may be used to this end are dis-closed in applicant's French Patent ~o. 75 00644 filed January 10, 1975, and laid open to public inspection on August 6, 1976.
jb/ - 5 -- ' , . .
1~4~J2~6 The invention will be more clearly understood in the light of the description herein below with reference to the appended drawings which show an embodiment of the invention by way of illustration, but not of limitation.
Fig. 1 shows a known device comprising a reference body arranged downstream of the measuring body.
Fig. 2 shows another known device comprising a reference body arranged upstream of the measuring body.
Fig. 3 represents the corona effect obtained when using a point to which a negative load is applied.
- Fig. 4 represents the corona effect when using a point to which a positive load is applied.
Fig. 5 shows means for controlling the corona effect by using a resistor.
Fig. 6 is a longitudinal section of the measuring cell.
Fig. 7 is a transverse section of the measuring and reference cells.
Figures 1 and 2 schematically show two known devices for measuring the mass of the particles of an aerosol per volume unit. According to each one of these Figures, a metallic point 1 is arranged with its axis perpendicular to a planar surface 2 of a measuring body 3. The surface 2 is partially covered by a planar receiving electrode 4. The measuring body 3 has a resonance frequency which varies as the configuration of body 3 varies, especially due to the formation of a deposit of particles on planar electrode 4.
Point 1 is connected to a negative terminal of a very high voltage current source 5. Planar electrode 4 is connected to means for measuring - . . : . .
-, .
.
- : .... . , . - . ~ .
~4~iZf~6 the resonance frequency of measuring body 3, said means being constituted e.g. by an oscillator 6.
The end 7 of point 1 is located at a distance d from the planar electrode 4, said distance d being greater than the sparking distance in the air for the high voltage current used in the device.
Figure 1 shows an embodiment in which point 1 and measur;ng body 3 are arranged in a coaxial measuring conduit 8. Conduit 8 comprises an air inlet nozzle 9 opening near the end 7 of point 1, as well as an aperture 10 opening into the atmosphere, which is associated with a metering pump 11.
Figure 2 shows a similar arrangement wherein the end 7 of point 1 is -located at a distance d from planar electrode 4 which partially covers the planar surface 2 of the measuring body 3, However in this embod;ment the reference body 3' is arranged in a reference conduit 8' constituting the lateral prolongation of the measuring conduit 8 and communicating with the latter by a passage 12. ~:
In the devices according to Figures 1 and 2, point 1 is connected to the negative terminal of an electric current source 5 delivering a current of very high voltage, the receiving electrode 4 covering a portion of the planar surface 2 of measuring body 3 being connected to oscillator 6. A
receiving electrode 4' covering a portion of planar surface 2' of reference body 3' is connected to an oscillator 6'.
The following comments may be made with respect to these two devices :
1) The reference body, which is arranged downstream of the measuring body, with reference to the direction of the air flow, receives aerosol particles which could not settle on the measuring body, or aerosol particles ,, . . , , , . , , ,~, .
. ' ~ . '' , :
.
which have eventually been detached from the measuring body.
Various devices are known which make use of the fact that certain substances have the property to present a determined resonance frequency for a given geometric configuration, said resonance frequency being bound to vary when the configuration is modified, especially under the effect of a deposit of particles. In these known devices the deposit of moving aerosol particles on a planar surface of a body, called measuring body, is caused by the passage of a high voltage electric current, between a metallic point and the planar surface of the measuring body, said surface being perpendicular to the axis of the aforementioned point and being ~ partially covered by a planar receiving electrode. The end of the pointi is separated from the planar surface by a distance greater than the spark ~ length in the atmosphere. In these devices the resonance frequency of ! 15 the measuring body is compared to the resonance frequency of a reference ! body maintained in similar temperature and pressure conditions and on the surface of which no deposit is formed.
In the various types of known devices, the reference body is placed in the clrcuit of derived air, and there is a risk of formation of a residual deposit which may modify the configuration of the reference body.
Furthermore, the air flow is initiated by a suction pump which ~s generally ~ arranged at the end of the circuit; the output rate of such an installation j may undergo the influence of variations which are independent from the ! ~ rate of precipitation of the particles.
¦ 25 In these same devices the metallic point is connected to the negative ~ -~: :
1 -2- ; ~ -' ' ' ~, .
, . .. - , , . ,,, . . . .. ~ . : ..
104(~266 terminal of a high voltage electric current generator and the planar receiving electrode is connected to measuring means adapted to measure the resonance frequency of the measuring body. On account of this arrangement, fractions of material are detached from the point, which results in modifying the configuration of the latter. These modifications of the configuration of the point result, in turn, in modifications of the intensity of the dispensed current, these latter modifications causing generally the efficiency of particle precipitation on the planar surface of the measuring body to decrease. Nothing can prevent these current intensity variations from occurring, since the high voltage current sources are voltage-controlled, but not intensity-controlled.
The instant invention allows these drawbacks to be overcome. By connecting the point to the positive terminal, the induced air flow, which is also called "electrical air flow" or "electrical wind" and which may occur in the known devices becomes sufficiently powerful so that it is no longer necessary to rely on the action of a suction pump, especially when taking into account the fact that the passage through which flow the air loaded with aerosol particles has been designed in such a manner that the pressure losses are reduced to a minimum.
When the point is connected to the positive terminal of the high voltage generator, the configuration of said point changes very slowly? and thus the resulting current variations are minimized. Nevertheless, with a view to obtain a still more constant deposit formation efficiency, it is advantageous to provide a current intensity control or regulation of the -feeding current.
: , ' , ' ' ' ~ '.'' .. . . .
. : ... : . , '. ', , ' - . .', . ~,'. . - . ... ~ . . .
lU4~;6 A device for measuring the mass of the particles of an aerosol per volume unit comprises :
- a solid body, or measuring body, having a resonance frequency and comprising a planar surface partially covered by a planar particle receiving electrode, said resonance frequency being a function of the mass of the deposited particles;
- measuring means for measuring the resonance frequency of said solid measuring body, especially as compared to the resonance frequency of a second solid body, or reference body, having the same characteristics as said measuring body and being maintained in the same temperature and pressure conditions as said measuring body;
- means for generating a flow of air loaded with particles and for directing said air flow toward said planar receiving electrode; and - means for electrically loading said particles with a polarity opposed to that of the planar receiving electrode.
In the device according to the invention the means for generating a flow of air loaded with particles and for directing said air flow toward the planar receiving electrode, as well as the means for electrically loading said particles with a polarity opposite to that of said planar receiving electrode are constitùted by a metallic point the geometrical axis of which is perpendicular to said planar receiving electrode, and which is separated from said planar receiving electrode by a distance of about 3 to 15 mm, said point being connected to the positive terminal of a source of electric current delivering a direct current of very high voltage, whereas said planar receiving electrode is connected to measuring means adapted to measure :
. : .
, . ,, -- . . . . . - - ..
, - - , - .: : ..
- . . . - . . . . .
, the resonance frequency of said measuring body, said point and said measuring body being arranged within a measuring conduit coaxial to said point, said measuring conduit com-prising an air inlet nozzle opening near the end of said point, an axial aperture opening into the atmosphere being provided at a location opposite said point, and the assembly of said measuring body,said point and said measuring conduit constituting a measuring cell.
The solid reference body may be arranged in a space called reference space which is entirely closed, and which may be constituted by a conduit similar to the measuring conduit or by a conduit having the same characteristicæ as those of said measuring conduit, the air inlet nozzle and the axial aperture being closed ~n these various embodiments.
When the reference space is constituted by a cell having the same characteristics as those of the measuring cell the air inlet nozzle and the axial aperture of which are closed, it is possible, too, to u~e alternatively each - one of said cells as a measuring cell or as a reference cell. Due to this possibility the instant device presents a considerable flexibility of use and optimum control and calibrating capacities.
In a preferred embodiment the direct current source is provided, for each cell, with current intensity control means regulating the delivered current, said control means comprising more particularly means for maintaining said current intensity at a constant value. Convenient control means of this kind which may be used to this end are dis-closed in applicant's French Patent ~o. 75 00644 filed January 10, 1975, and laid open to public inspection on August 6, 1976.
jb/ - 5 -- ' , . .
1~4~J2~6 The invention will be more clearly understood in the light of the description herein below with reference to the appended drawings which show an embodiment of the invention by way of illustration, but not of limitation.
Fig. 1 shows a known device comprising a reference body arranged downstream of the measuring body.
Fig. 2 shows another known device comprising a reference body arranged upstream of the measuring body.
Fig. 3 represents the corona effect obtained when using a point to which a negative load is applied.
- Fig. 4 represents the corona effect when using a point to which a positive load is applied.
Fig. 5 shows means for controlling the corona effect by using a resistor.
Fig. 6 is a longitudinal section of the measuring cell.
Fig. 7 is a transverse section of the measuring and reference cells.
Figures 1 and 2 schematically show two known devices for measuring the mass of the particles of an aerosol per volume unit. According to each one of these Figures, a metallic point 1 is arranged with its axis perpendicular to a planar surface 2 of a measuring body 3. The surface 2 is partially covered by a planar receiving electrode 4. The measuring body 3 has a resonance frequency which varies as the configuration of body 3 varies, especially due to the formation of a deposit of particles on planar electrode 4.
Point 1 is connected to a negative terminal of a very high voltage current source 5. Planar electrode 4 is connected to means for measuring - . . : . .
-, .
.
- : .... . , . - . ~ .
~4~iZf~6 the resonance frequency of measuring body 3, said means being constituted e.g. by an oscillator 6.
The end 7 of point 1 is located at a distance d from the planar electrode 4, said distance d being greater than the sparking distance in the air for the high voltage current used in the device.
Figure 1 shows an embodiment in which point 1 and measur;ng body 3 are arranged in a coaxial measuring conduit 8. Conduit 8 comprises an air inlet nozzle 9 opening near the end 7 of point 1, as well as an aperture 10 opening into the atmosphere, which is associated with a metering pump 11.
Figure 2 shows a similar arrangement wherein the end 7 of point 1 is -located at a distance d from planar electrode 4 which partially covers the planar surface 2 of the measuring body 3, However in this embod;ment the reference body 3' is arranged in a reference conduit 8' constituting the lateral prolongation of the measuring conduit 8 and communicating with the latter by a passage 12. ~:
In the devices according to Figures 1 and 2, point 1 is connected to the negative terminal of an electric current source 5 delivering a current of very high voltage, the receiving electrode 4 covering a portion of the planar surface 2 of measuring body 3 being connected to oscillator 6. A
receiving electrode 4' covering a portion of planar surface 2' of reference body 3' is connected to an oscillator 6'.
The following comments may be made with respect to these two devices :
1) The reference body, which is arranged downstream of the measuring body, with reference to the direction of the air flow, receives aerosol particles which could not settle on the measuring body, or aerosol particles ,, . . , , , . , , ,~, .
. ' ~ . '' , :
.
which have eventually been detached from the measuring body.
2) On account of the fact that the point has a negative potential, said point is rapidly deteriorated; this deterioration which may be easily observed results in an increase of the radius of curvature of said point.
The variation of the electric current intensity between the point and the electrode generally result in a progressive decrease of the efficiency of particle depositing on the electrode~
The variation of the electric current intensity between the point and the electrode generally result in a progressive decrease of the efficiency of particle depositing on the electrode~
3) Figure 3 schematically shows the distribution of the lines of current 14, called "corona effect", between a point 1 having a negative potential and a planar electrode orthogonal with respect to the axis of said point. These lines of current 14 which are represented by dashed lines, define a volume of tapered configuration, and the air surrounding the point is carried, in the form of air jets, 15 represented by pointed lines, along the flow path. The air contacts the electrode in the immediate vicinity of the median zone of the latter, and then diverges toward the periphery.
In this device, the aerosol particles are able to deposit in a reguliar manner on the median portion of the planar receiving electrode.
The attempt to obtain an optimum repartition of the particles on the sensitive electrode of the measuring body has led to designing the device according to Figure 4, wherein the lines of current 14 are assembled as shown by the dashed lines, as shown in Figure 3. It should be noted that in this case the "electric wind" becomes sufficient to ensure an output of about one litre per minute. Is is thus no longer necessary to operate a suction pump at the outlet of the measuring cell.
With a view to obtain;ng a regular air flow the intensity of the electric . , -, curreDt corresponding to the corona e~fect must be stabi-lized; this stabilisation is achieved by two means. In the first place, as shown in Figure 5, the resistor of about ten mega-Ohms connected in series with the feeding conductor of the point attenuates the intensity variations having very short periods. Furthermore, a device such as the intensity stabiliser for very high voltage current disclosed in the French patent No. 75 00644 allows of maintaining the current intensity at a predetermined value and of avoiding any deviation.
Figure 6 is a longitudinal section showing a measuring cell A or a reference cell B of a device according to the invention for measuring the mass of particles of an aerosol per volume unit.
A block 17 mass of plastic material having a high resistivity and a high dielectric coefficient, e.g. the material sold under the commercisl designation "ALTUGLAS" `~
is provided with a measuring conduit 8 of cylindrical cross-section. This measuring conduit comprises a plurality of coaxial sections, to wit : a section 8a having a small dia-meter as compared to its length and wherein a metallic point 1 ls fixed, a section 8b having a comparatively great diameter with respect to its length and which constitutes a discharge chamber wherein the measuring body 3 is arranged, said measuring body being constituted by a piezo-electric quartz blade perpendicular to the axis of conduit 8, and a section 8c the diameter of which is approximately equal to that of section 8a and which opens into the atmosphere through an aperture 10.
Point 1 comprises a plurality of cylindrical sections at least one ,~b/f~, - g _ ~ ~P4U2~;6 which (la) has a diameter equal to that of section 8a of conduit 8, and a frusto-conical terminal section lb made of tungsten steel or of stainless steel, the end of said frusto-conical section being preferentially made of tungsten.
Block 17 is a parallelepipedic body on which a prismatic relief portion is provided with a view to facilitating the provision of an air inlet nozzle 9 opening into section 8a near the conical end 7 of point lb.
With a view to facilitating the assembly and the dismounting of the measuring or reference cell, block 17 is divided into two portions 19 and 20 defined by a plane indicated at x-x and constituted in the embodiment according to Fig. 6 by the medium plane of the discharge chamber 8b. Once assembled, parts 19 and 20 are maintained in their relative position by means of screws (not shown).
Point 1 is connected to a positive terminal of a high-voltage current source 5 by means of a conductor 21 extending through body 19 and maintained in contact with point 1 on a cylindrical section of the latter.
Measuring body 3 is maintained in the medium zone of discharge chamber 8b by means of a supporting element 22. Measuring body 3 comprises a planar surface 2 located in front of the point and that planar surface 2 supports on a portion of its area, especially the medium portion thereof, a planar particle receiving electrode. Said planar electrode 4 as well as an electrode 23 applied to the opposite surface are connected by conductors 24 and 25 to an oscillator 6.
Fig. 7 is a sectional view taken in plane x-x of an assembly constituted by a measuring cell A and a reference cell B mounted in the vicinity of said ~ ~ . - . . - ~ - ' , .
-~ . . -, .
1~4~3Z~ô6 measuring cell. This Figure shows the sectional form of the discharge chamber 8bA of measuring cell A, which contains a piezo-electric quartz blade 3A having a circular periphery, and the section 8bB of reference 7B
containing a blade 3B which also has a circular periphery.
On each measuring body 3A, 3B, and in front of the point lA, lB, a circular electrode 26A, 26B is mounted in a position coaxial with respect to the corresponding measuring body 3A, 3B. The circular electrode 27A and 27B coaxial to the corresponding measuring body 3A and 3B is mounted on the face in front of point lA and lB. Plates 26A, 26B, 27A, 27B are connected, respectively, by conductors 25A, 24B, 24A, 25B to oscillators 6A and 6B corresponding, respectively, to cells A and B.
The output terminals of oscillators 6A and 6B are connected to a frequency mixer 28 the outlet of which is connected to a frequency-meter 29 comprising an indicating scale or recording means for indicating or recording the difference between the resonance frequencies of bodies 3A
and 3B, respectively.
In one embodiment of the device according to the invention for measuring the mass of particles of an aerosol per volume unit, wherein the point is connected to a current source of +10 000 Volts,said point being arranged at a distance d of 15 mm from the measuring electrode, the air flow rate due to the "electric wind" amounts to 1 1 tr/min.
The size of the captured aerosol particles is comprised between 0.01 and 50 microns.
The operations of comparison of the resonance frequencies of the measuring body and the resonance frequencies of the reference body are .
--.. ~ , ' .
1t~4~ t~ 6 effected in a cont;nuous manner, or stepwise in accordance with a selected timing sequence.
The indications obtained are accurate with a tolerance on the order of one Hertz.
The embodiment described hereinabove, which has allowed of obtaining the above-mentioned results is disclosed by way of illustration, but not of limitation.
- . : . .
, .
In this device, the aerosol particles are able to deposit in a reguliar manner on the median portion of the planar receiving electrode.
The attempt to obtain an optimum repartition of the particles on the sensitive electrode of the measuring body has led to designing the device according to Figure 4, wherein the lines of current 14 are assembled as shown by the dashed lines, as shown in Figure 3. It should be noted that in this case the "electric wind" becomes sufficient to ensure an output of about one litre per minute. Is is thus no longer necessary to operate a suction pump at the outlet of the measuring cell.
With a view to obtain;ng a regular air flow the intensity of the electric . , -, curreDt corresponding to the corona e~fect must be stabi-lized; this stabilisation is achieved by two means. In the first place, as shown in Figure 5, the resistor of about ten mega-Ohms connected in series with the feeding conductor of the point attenuates the intensity variations having very short periods. Furthermore, a device such as the intensity stabiliser for very high voltage current disclosed in the French patent No. 75 00644 allows of maintaining the current intensity at a predetermined value and of avoiding any deviation.
Figure 6 is a longitudinal section showing a measuring cell A or a reference cell B of a device according to the invention for measuring the mass of particles of an aerosol per volume unit.
A block 17 mass of plastic material having a high resistivity and a high dielectric coefficient, e.g. the material sold under the commercisl designation "ALTUGLAS" `~
is provided with a measuring conduit 8 of cylindrical cross-section. This measuring conduit comprises a plurality of coaxial sections, to wit : a section 8a having a small dia-meter as compared to its length and wherein a metallic point 1 ls fixed, a section 8b having a comparatively great diameter with respect to its length and which constitutes a discharge chamber wherein the measuring body 3 is arranged, said measuring body being constituted by a piezo-electric quartz blade perpendicular to the axis of conduit 8, and a section 8c the diameter of which is approximately equal to that of section 8a and which opens into the atmosphere through an aperture 10.
Point 1 comprises a plurality of cylindrical sections at least one ,~b/f~, - g _ ~ ~P4U2~;6 which (la) has a diameter equal to that of section 8a of conduit 8, and a frusto-conical terminal section lb made of tungsten steel or of stainless steel, the end of said frusto-conical section being preferentially made of tungsten.
Block 17 is a parallelepipedic body on which a prismatic relief portion is provided with a view to facilitating the provision of an air inlet nozzle 9 opening into section 8a near the conical end 7 of point lb.
With a view to facilitating the assembly and the dismounting of the measuring or reference cell, block 17 is divided into two portions 19 and 20 defined by a plane indicated at x-x and constituted in the embodiment according to Fig. 6 by the medium plane of the discharge chamber 8b. Once assembled, parts 19 and 20 are maintained in their relative position by means of screws (not shown).
Point 1 is connected to a positive terminal of a high-voltage current source 5 by means of a conductor 21 extending through body 19 and maintained in contact with point 1 on a cylindrical section of the latter.
Measuring body 3 is maintained in the medium zone of discharge chamber 8b by means of a supporting element 22. Measuring body 3 comprises a planar surface 2 located in front of the point and that planar surface 2 supports on a portion of its area, especially the medium portion thereof, a planar particle receiving electrode. Said planar electrode 4 as well as an electrode 23 applied to the opposite surface are connected by conductors 24 and 25 to an oscillator 6.
Fig. 7 is a sectional view taken in plane x-x of an assembly constituted by a measuring cell A and a reference cell B mounted in the vicinity of said ~ ~ . - . . - ~ - ' , .
-~ . . -, .
1~4~3Z~ô6 measuring cell. This Figure shows the sectional form of the discharge chamber 8bA of measuring cell A, which contains a piezo-electric quartz blade 3A having a circular periphery, and the section 8bB of reference 7B
containing a blade 3B which also has a circular periphery.
On each measuring body 3A, 3B, and in front of the point lA, lB, a circular electrode 26A, 26B is mounted in a position coaxial with respect to the corresponding measuring body 3A, 3B. The circular electrode 27A and 27B coaxial to the corresponding measuring body 3A and 3B is mounted on the face in front of point lA and lB. Plates 26A, 26B, 27A, 27B are connected, respectively, by conductors 25A, 24B, 24A, 25B to oscillators 6A and 6B corresponding, respectively, to cells A and B.
The output terminals of oscillators 6A and 6B are connected to a frequency mixer 28 the outlet of which is connected to a frequency-meter 29 comprising an indicating scale or recording means for indicating or recording the difference between the resonance frequencies of bodies 3A
and 3B, respectively.
In one embodiment of the device according to the invention for measuring the mass of particles of an aerosol per volume unit, wherein the point is connected to a current source of +10 000 Volts,said point being arranged at a distance d of 15 mm from the measuring electrode, the air flow rate due to the "electric wind" amounts to 1 1 tr/min.
The size of the captured aerosol particles is comprised between 0.01 and 50 microns.
The operations of comparison of the resonance frequencies of the measuring body and the resonance frequencies of the reference body are .
--.. ~ , ' .
1t~4~ t~ 6 effected in a cont;nuous manner, or stepwise in accordance with a selected timing sequence.
The indications obtained are accurate with a tolerance on the order of one Hertz.
The embodiment described hereinabove, which has allowed of obtaining the above-mentioned results is disclosed by way of illustration, but not of limitation.
- . : . .
, .
Claims (10)
1.- A device for measuring the mass of particles of an aerosol per volume-unit which comprises :
- a solid measuring body having a resonance frequency and comprising a planar surface partially covered by a planar particle receiving electrode, said resonance frequency being a function of the mass of the deposited particles;
- measuring means for measuring the resonance frequency of said solid measuring body, especially as compared to the resonance frequency of a second solid body, or reference body, having the same characteristics as said measuring body and being maintained in the same temperature and pressure conditions as said measuring body;
- means for generating a flow of air loaded with particles and for directing said air flow toward said planar receiving electrode; and - means for electrically loading said particles with a polarity opposed to that of the planar receiving electrode, in which device said means for generating a flow of air loaded with particles and for directing said air flow toward the planar receiving electrode, as well as the means for electrically loading said particles with a polarity opposite to that of said planar receiving electrode are constituted by a metallic point the geometrical axis of which is perpendicular to said planar receiving electrode, and which is separated from said planar receiving electrode by a distance of about 3 to 15 mm, said point being connected to the positive terminal of a source of electric current delivering a direct current of very high voltage, whereas said planar receiving electrode is connected to measuring means adapted to measure the resonance frequency of said measuring body, said point and said measuring body being arranged within a measuring conduit coaxial to said point, said measuring conduit comprising an air inlet nozzle opening near the end of said point, an axial aperture opening into the atmosphere being provided at a location opposed to said point, and the assembly of said measuring body, said point and said measuring conduit constituting a measuring cell.
- a solid measuring body having a resonance frequency and comprising a planar surface partially covered by a planar particle receiving electrode, said resonance frequency being a function of the mass of the deposited particles;
- measuring means for measuring the resonance frequency of said solid measuring body, especially as compared to the resonance frequency of a second solid body, or reference body, having the same characteristics as said measuring body and being maintained in the same temperature and pressure conditions as said measuring body;
- means for generating a flow of air loaded with particles and for directing said air flow toward said planar receiving electrode; and - means for electrically loading said particles with a polarity opposed to that of the planar receiving electrode, in which device said means for generating a flow of air loaded with particles and for directing said air flow toward the planar receiving electrode, as well as the means for electrically loading said particles with a polarity opposite to that of said planar receiving electrode are constituted by a metallic point the geometrical axis of which is perpendicular to said planar receiving electrode, and which is separated from said planar receiving electrode by a distance of about 3 to 15 mm, said point being connected to the positive terminal of a source of electric current delivering a direct current of very high voltage, whereas said planar receiving electrode is connected to measuring means adapted to measure the resonance frequency of said measuring body, said point and said measuring body being arranged within a measuring conduit coaxial to said point, said measuring conduit comprising an air inlet nozzle opening near the end of said point, an axial aperture opening into the atmosphere being provided at a location opposed to said point, and the assembly of said measuring body, said point and said measuring conduit constituting a measuring cell.
2.- A device according to claim 1, wherein said reference body is arranged within an entirely closed reference space.
3.- A device according to claim 2, wherein said reference space is defined by a conduit similar to the measuring conduit, its air inlet nozzle and axial aperture being closed.
4.- A device according to claim 2, wherein the reference space is constituted by a conduit having the same characteristics as those of the measuring conduit, its air inlet nozzle and axial aperture being closed.
5.- A device according to claim 2, wherein said reference space is constituted by a cell having the same characteristics as those of the measuring cell, its air inlet nozzle and axial aperture being closed.
6.- A device according to claim 1, wherein the direct current source is provided with means for controlling the intensity of the supplied electric current, said control means comprising more particularly means for maintaining said current intensity at a constant value.
7.- A device according to claim 6, wherein said reference body is arranged within an entirely closed reference space.
8.- A device according to claim 7, wherein said reference space is constituted by a conduit similar to the measuring conduit, its air inlet nozzle and axial aperture being closed.
9.- A device according to claim 7, wherein the reference space is constituted by a conduit having the same characteristics as those of the measuring conduit, its air inlet nozzle and axial aperture being closed.
10.- A device according to claim 7, wherein the reference space is constituted by a cell having the same characteristics as those of the measuring cell, its air inlet nozzle and axial aperture being closed.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR7501128A FR2298099A1 (en) | 1975-01-15 | 1975-01-15 | DEVICE FOR MEASURING THE MASS OF PARTICLES OF AN AEROSOL PER UNIT OF VOLUME |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1040266A true CA1040266A (en) | 1978-10-10 |
Family
ID=9149816
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA243,196A Expired CA1040266A (en) | 1975-01-15 | 1976-01-08 | Device for measuring the mass of particles of an aerosol per volume unit |
Country Status (13)
| Country | Link |
|---|---|
| US (1) | US4041768A (en) |
| JP (1) | JPS5196358A (en) |
| BE (1) | BE837413A (en) |
| CA (1) | CA1040266A (en) |
| CH (1) | CH593490A5 (en) |
| DE (1) | DE2559097A1 (en) |
| DK (1) | DK7376A (en) |
| ES (1) | ES444186A1 (en) |
| FR (1) | FR2298099A1 (en) |
| GB (1) | GB1502521A (en) |
| IT (1) | IT1054090B (en) |
| LU (1) | LU74141A1 (en) |
| NL (1) | NL7600270A (en) |
Families Citing this family (20)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2452452A1 (en) * | 1979-03-29 | 1980-10-24 | Prestinox Sa | Refinement to drive mechanism of film or tape reels - provides electromagnetically operated controlled braking of reel spindles |
| US4312180A (en) * | 1979-09-28 | 1982-01-26 | Battelle Development Corporation | Detecting particles |
| SE8105923L (en) * | 1981-10-07 | 1983-04-08 | Boliden Ab | SET TO INDICATE HIDDEN SKILLS |
| CH662421A5 (en) * | 1983-07-13 | 1987-09-30 | Suisse Horlogerie Rech Lab | PIEZOELECTRIC CONTAMINATION DETECTOR. |
| US4670137A (en) * | 1986-01-27 | 1987-06-02 | Hitachi, Ltd. | Impurity detector |
| US6077334A (en) * | 1995-01-17 | 2000-06-20 | Joannou; Constantinos J. | Externally ionizing air filter |
| GB9523812D0 (en) * | 1995-11-21 | 1996-01-24 | Sun Electric Uk Ltd | Method and apparatus for analysis of particulate content of gases |
| US5948141A (en) * | 1997-09-30 | 1999-09-07 | Hewlett-Packard Company | Method and apparatus for purification of a discharge gas |
| DE10000608C2 (en) * | 2000-01-10 | 2002-05-23 | Max Planck Gesellschaft | Method and device for detecting the relative impact positions of microparticles |
| RU2182523C1 (en) * | 2001-02-08 | 2002-05-20 | Общество с ограниченной ответственностью "ВИНТЕЛ" | Device for accumulating of aerosols from gases |
| US6807874B2 (en) * | 2002-01-21 | 2004-10-26 | Shimadzu Corporation | Collecting apparatus of floating dusts in atmosphere |
| DE20203999U1 (en) * | 2002-03-13 | 2002-08-22 | Solvay Fluor & Derivate | Device for determining the physical and chemical parameters of aerosol formulations from metered dose aerosols |
| JP2003337087A (en) * | 2002-05-20 | 2003-11-28 | Shimadzu Corp | Apparatus for collecting suspended particle |
| US7704302B2 (en) * | 2007-02-27 | 2010-04-27 | General Electric Company | Electrostatic precipitator having a spark current limiting resistors and method for limiting sparking |
| US8167986B2 (en) * | 2008-07-23 | 2012-05-01 | Board Of Supervisors Of Louisiana State University And Agricultural And Mechanical College | Airborne particulate sampler |
| WO2014153142A1 (en) | 2013-03-14 | 2014-09-25 | Colorado Seminary, Which Owns And Operates The University Of Denver | Mems aerosol impactor |
| EP2773941A1 (en) * | 2011-11-04 | 2014-09-10 | Danmarks Tekniske Universitet | Resonant fiber based aerosol particle sensor and method |
| CN104390875B (en) * | 2013-12-31 | 2017-02-15 | 北京至感传感器技术研究院有限公司 | Portable detector with modified PM2.5 cutting head |
| WO2015180981A1 (en) * | 2014-05-30 | 2015-12-03 | Koninklijke Philips N.V. | Aerosol particle mass sensor and sensing method |
| EP4336151A1 (en) * | 2022-09-12 | 2024-03-13 | Consejo Superior de Investigaciones Científicas (CSIC) | Nanomechanical mass flow meter and controller device, method, and associated uses thereof |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3114877A (en) * | 1956-10-30 | 1963-12-17 | Gen Electric | Particle detector having improved unipolar charging structure |
| US3449667A (en) * | 1966-05-18 | 1969-06-10 | Gourdine Systems Inc | Electrogasdynamic method and apparatus for detecting the properties of particulate matter entrained in gases |
| DE1679532B1 (en) * | 1967-10-09 | 1970-12-10 | Berckheim Graf Von | Arrangement for generating unipolar air ions |
| US3561253A (en) * | 1969-03-26 | 1971-02-09 | Thermo Systems Inc | Apparatus and method of measurement of particulate mass |
| US3653253A (en) * | 1970-01-05 | 1972-04-04 | Thermo Systems Inc | Aerosol mass concentration spectrometer |
| US3715911A (en) * | 1970-05-11 | 1973-02-13 | Susquehanna Corp | Apparatus for sensing air-borne particulate matter |
| US3679973A (en) * | 1970-10-20 | 1972-07-25 | Us Interior | Electrogasdynamic dust monitor |
| US3879986A (en) * | 1973-10-05 | 1975-04-29 | Atomic Energy Commission | Parallel point to plane electrostatic precipitator particle size sampler |
-
1975
- 1975-01-15 FR FR7501128A patent/FR2298099A1/en active Granted
- 1975-12-29 CH CH1681075A patent/CH593490A5/xx not_active IP Right Cessation
- 1975-12-30 DE DE19752559097 patent/DE2559097A1/en not_active Ceased
-
1976
- 1976-01-07 US US05/647,066 patent/US4041768A/en not_active Expired - Lifetime
- 1976-01-08 GB GB641/76A patent/GB1502521A/en not_active Expired
- 1976-01-08 LU LU74141A patent/LU74141A1/xx unknown
- 1976-01-08 CA CA243,196A patent/CA1040266A/en not_active Expired
- 1976-01-08 BE BE6045325A patent/BE837413A/en not_active IP Right Cessation
- 1976-01-09 DK DK7376*#A patent/DK7376A/en not_active Application Discontinuation
- 1976-01-09 ES ES444186A patent/ES444186A1/en not_active Expired
- 1976-01-09 JP JP51002392A patent/JPS5196358A/ja active Pending
- 1976-01-12 NL NL7600270A patent/NL7600270A/en not_active Application Discontinuation
- 1976-01-15 IT IT19280/76A patent/IT1054090B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| LU74141A1 (en) | 1976-07-20 |
| DE2559097A1 (en) | 1976-07-22 |
| ES444186A1 (en) | 1978-03-16 |
| FR2298099A1 (en) | 1976-08-13 |
| FR2298099B1 (en) | 1978-12-29 |
| GB1502521A (en) | 1978-03-01 |
| CH593490A5 (en) | 1977-12-15 |
| US4041768A (en) | 1977-08-16 |
| DK7376A (en) | 1976-07-16 |
| NL7600270A (en) | 1976-07-19 |
| BE837413A (en) | 1976-07-08 |
| IT1054090B (en) | 1981-11-10 |
| JPS5196358A (en) | 1976-08-24 |
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